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Peptide Structure and Analysis
Published in Marco Chinol, Giovanni Paganelli, Radionuclide Peptide Cancer Therapy, 2016
Carlo Pedone, Giancarlo Morelli, Diego Tesauro, Michele Saviano
From the chemical point of view peptides are formed when two or more amino acid residues are condensed together, leading to a secondary amide bond, and, consequently, to a peptide unit. Peptides are, then, chains of a certain number of covalently linked amino acid residues, each of which is intrinsically asymmetric because of the optically active α-carbon atoms. The amino acid sequence along the chain, the spatial configuration of the asymmetric Cα atoms of each residue, and the local conformation of part of the molecule or the overall conformation of the entire peptide, together with the intra-molecular and intermolecular interactions of various types, are all important factors in determining the biological activity and the mechanism of its action.
Protein/Peptide Sequence Analysis by Mass Spectrometry
Published in Ajit S. Bhown, Protein/Peptide Sequence Analysis: Current Methodologies, 1988
The dipeptides are then converted to their trimethylsilyl derivatives in the same vial using bis(trimethylsilyl)trifluoroacetamide;73,74 no transfer of material is necessary. When trime-thylsilylation is carried out, the active hydrogens of amino, carboxyl, imidazoyl, indolyl, primary amide, and guanido groups react.76 One proton on the α-amino, primary amido, and aminoethyl-Cys is exchanged, both protons on the α-amino Gly and ϵ-amino Lys groups are replaced, and three of the four protons of the guanido group of Arg are displaced. Protons of the secondary amide group of dipeptides generally do not react, but protons of the ring NH groups in diketopiperazines react. During trimethylsilylation, dipeptides containing N-terminal Asp usually form cyclic imides, and some Gly-X (X = Gly, Ala, Met, Gln, Glu) dipeptides form diketopiperazines.
Ethosome as antigen delivery carrier: optimisation, evaluation and induction of immunological response via nasal route against hepatitis B
Published in Journal of Microencapsulation, 2022
Akash Raghuvanshi, Kamal Shah, Hitesh Kumar Dewangan
Interaction between antigen with different excipients were confirmed by FTIR spectroscopy (Figure 2). There is no physical interaction between antigen and excipients established by the graph of ethosome formulation and physical mixture (antigen + soya lecithin + ethanol). The graph of the ethosome formulation was almost resemble to physical mixture of excipient, and the formulation have no specific peaks which proof the non-interaction of the formulation. The FTIR spectrum of lecithin showed evidence of methylation, particularly in the 1700–1200 cm−1 region. A new peak appeared at the high wave number, 1736 cm−1, which was attributed to the quaternary ammonium salt (physical mixture graph). In the spectrum of antigen loaded ethosome, the tip of the peak at 3267 cm−1 was wider, which indicated enhanced hydrogen bonding. The strong, broad peaks in 3267 cm−1 region and a sharp peak at 2921 cm−1 were also observed. A new peak represented at 1710 cm−1 was attributed to C = O stretching. The FTIR spectra were consistent with the modification of propylene glycol film by soya lecithin. In formulation showed the characteristic peaks of the substituted secondary amide in the 3300–3400 cm−1 region. The peaks at 1093 and 600 cm−1 were attributed to the C–S stretching vibrations.
Mechanistic and biological characterisation of novel N 5-substituted paullones targeting the biosynthesis of trypanothione in Leishmania
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Andrea Medeiros, Diego Benítez, Ricarda S. Korn, Vinicius C. Ferreira, Exequiel Barrera, Federico Carrión, Otto Pritsch, Sergio Pantano, Conrad Kunick, Camila I. de Oliveira, Oliver C. F. Orban, Marcelo A. Comini
For paullones containing an acetamide linker, high activities (IC50 = 0.5–0.8 µM) were observed for derivatives with small N-alkyl substituents. A secondary amide (N-methylacetamide, 9) as well as tertiary amides (N,N-dimethylacetamide, 10 and N,N-diethylacetamide, 12) proved active, which implies that an H-bond donor at this position is not essential for inhibitor-enzyme interaction. The primary acetamide (7), the acetohydrazide (8) or amino-substituted paullone (11) and the analogues containing terminal hydroxyl functions (13, 14) or the bulkier tert-butylacetamide group (15), retained low µM activity (IC50 = 1.5–5.2 µM). In contrast, the activity was significantly impaired for analogues containing terminal heterocyclic (i.e. 1,3,4-thiadiazole, 4,5-dihydro-1,3,thiazole, 1,3-oxazole, IC50 = 20–30 µM for 16, 17, 18, respectively) or phenyl (IC50 ∼30 µM for 19) rings.
Design of temozolomide-loaded proliposomes and lipid crystal nanoparticles with industrial feasible approaches: comparative assessment of drug loading, entrapment efficiency, and stability at plasma pH
Published in Journal of Liposome Research, 2021
Tejashree Waghule, Vamshi Krishna Rapalli, Gautam Singhvi, Srividya Gorantla, Archana Khosa, Sunil Kumar Dubey, Ranendra Narayan Saha
The FTIR spectrum obtained for the pure drug is shown in Figure. 5. The characteristic strong peak for carbonyl amide was found at 1680–1630 cm−1 thus confirming the presence of amide. The N-H band for secondary amide was observed at 3300 cm−1. The N-H stretch for primary amide was seen as a doublet in the range of 3350 and 3180 cm−1. The N-H bending band at 1640–1620 cm−1 is found to partially overlap the carbonyl band. Other bands like N = N stretching at 1577 cm−1 and C-N stretching at 1400 cm−1 were also observed. The overlay of pure drug, proliposomes and the lyophilized LCNPs was obtained as in Figure 6. No major interaction between the excipients and the drug was observed.